Attempts stall, Idle Pulses 600-800 rpms, horrible MPG

[wiswind]

The humidity issue that you mention gets me thinking about the spark plug wires.
However, I don't see how that would impact your fuel economy when the motor is running smoothly.....

I cannot remember if you replaced your upstream (before catalytic converter) oxygen sensors or not.
I hate to suggest them, as that is another $130-ish guess.
If you have not....and decide to replace them.....I would spend the extra few bucks and get the genunie Motorcraft brand.
I have read that they may be made by Bosch......but I would STILL get the Motorcraft as they will be made to the Motorcraft Specifications.
It is a long shot.....but the fact that the vehicle seems to be running great (except for the humid weather starting) and just giving you very low fuel economy......wondering if somehow the oxygen sensors are getting you to run the incorrect air fuel ratio.

HOWEVER, if you have an electrical gremlin......that might cause whatever reference voltage that the PCM is using to compare to be off......and give you the wrong value.
I believe that the heated oxygen sensor GENERATES a voltage.......which the PCM is monitoring....comparing it to some stored value that would determine when the ideal air fuel ratio is being met.

Again.....I am just brain storming.......

[tripletdaddy]

More symptoms is good. Perhaps the "problem" is getting bad enough it can be diagnosed, located and repaired. Too tired to read the latest posts on this page. I only got through Selectron's. Ditto on the voltage on the red wire, VPWR, to all of the EEC stuff. While checking the voltage all over, you should do the "wiggle" test while you're at it. That would be wiggling the connecting wiring between your positive probe and the engine fuse box, with the negative probe firmly to battery ground. Pull off component connectors to front probe them for power. I think you can also back probe them too, though you may miss a weak point if it's in the connector. At this point, I have no ideas with the new symptoms.

What threads did you talk about your hot start problems?

There are two temperature sensors you probably already know. The ECT sensor, for the computer to set the fuel/air ratio and turning on and off the radiator fans, is located at the back of the engine, screwed into an elbow that feeds the heater hose. This is just forward and above the upper radiator hose. A two wire connector goes to it. The dash temp gauge sending unit is about six inches behind the ECT and buried behind and under a bunch of stuff, screwed into the intake manifold. It's just to the right of the back fuel injector, I think #3. It has a single wire to it, typically with a 90 degree boot.

[searcherrr]

Originally Posted by wiswind

The humidity issue that you mention gets me thinking about the spark plug wires.
However, I don't see how that would impact your fuel economy when the motor is running smoothly.....

I cannot remember if you replaced your upstream (before catalytic converter) oxygen sensors or not.
I hate to suggest them, as that is another $130-ish guess.
If you have not....and decide to replace them.....I would spend the extra few bucks and get the genunie Motorcraft brand.
I have read that they may be made by Bosch......but I would STILL get the Motorcraft as they will be made to the Motorcraft Specifications.
It is a long shot.....but the fact that the vehicle seems to be running great (except for the humid weather starting) and just giving you very low fuel economy......wondering if somehow the oxygen sensors are getting you to run the incorrect air fuel ratio.

HOWEVER, if you have an electrical gremlin......that might cause whatever reference voltage that the PCM is using to compare to be off......and give you the wrong value.
I believe that the heated oxygen sensor GENERATES a voltage.......which the PCM is monitoring....comparing it to some stored value that would determine when the ideal air fuel ratio is being met.

Again.....I am just brain storming.......

I haven't replaced the plug wires since about 10k ago when my now "old new plugs" were put in. I haven't tried the "at night open hood and watch for fireworks" test either. I guess I should as thats pretty easy. I'm gonna use a spray bottle of water for a mist to test with too.

Yeah, I was wondering about the same thing you said Wiswind... regarding the Upstream O2's. I had said a few times here that I was gonna replace them, and never did. I have 2 on hand and they are the exact Bosch part number of the OEM's, but they are not from Ford/Motorcraft. A long time ago I had put all 4 new ones in there (prior to the PCM wiring fix) and the engine near stalling blip still presented itself, so I took'em out, cleaned them up and brought'em back to the store.

Electrical gremlin and reference voltage. Yes.... I'm really leaning to this at the moment. There are a great number of reasons for me to suspect this which support my "Electrical Chaos" theory. I think what I need to do is while the van is running, go jostle the wiring harness where it was repaired so I can make myself feel better about that wiring being "OK" to use... and just see if the engine does anything symptomatic.

I know the rear O2's don't supply A/F ratio information to the PCM, but they are Catalyst monitors.... but I swear I saw the other day that Catalyst Monitoring test had not completed in my OBDII program. Later I saw it was completed and its been COMPLETED ever since I've looked at it again on subsequent tests.

[Selectron]

You were asking about the wire colours for the VPWR feeds off of the switched contacts of the PCM power relay and through the various splice points, so just confirming that they are all coloured red, without exception. I don't have the Ford CD/DVD for the Windstar by the way so I'm working from a different set of diagrams (PDF format). Those Ford CDs can be really cumbersome to navigate so you might want to take a look at these and see if they're any easier to follow:

'95 Windstar PCM & engine controls, diagram 1 of 4
'95 Windstar PCM & engine controls, diagram 2 of 4
'95 Windstar PCM & engine controls, diagram 3 of 4
'95 Windstar PCM & engine controls, diagram 4 of 4

'95 Windstar wiring diagram - cooling fans

[searcherrr]

Thanks Selectron. I'll look at those in a bit. Today I'm going to remove the ICM and have it tested. If it shows up good, I'll come back and get on the next step with checking DCV throughout the vehicle and use your charts instead of the CD-ROM program..... cause YES.... I much rather browse through a PDF than that damn cd-rom.

Thanks for your time in posting that stuff.

[searcherrr]

Also working in these threads at the moment too:
"Speedometer Driven Gear" vs "New Drive Gear"
http://www.automotiveforums.com/vbul...89#post6000889

"Rear of van sitting slanted down to right"
New problem which may or may not be related to the bad MPG:
http://www.automotiveforums.com/vbul...=1#post6000798

[wiswind]

The rear oxygen sensor test takes the longest of all the tests to complete.
Since I put the Walker catalytic conveters on.....I think that it has made it take a LOT longer to complete.
However, it is a Pass/fail type of monitoring.....which is not used to control the motor....as long as there is not a FAIL indication.
The upstream ones, however, are the ones that tell the computer what the air/fuel ratio is.....and this is a value that is constantly changing......basically cycling very fast between slightly lean to slightly rich.....
As the oxygen sensor ages....the switching speed slows slightly, HOWEVER, if it becomes too slow, the computer WILL light the CEL and set a code that specifically states that the switching speed is too slow.

[searcherrr]

Thanks Wiswind. I've never seen a "Failed." I just saw a grayed out "Not Completed."

================================================== ==
How does the reporting of vehicle speed happen?

Are there wheel speed sensors besides the VSS?

Is it possible to have one of the wrong speedometer driven gear or the other drive gear and still get the right vehicle speed reported?

Which of the two gears involved with the speedo and VSS would be responsible for bad MPG if the wrong gear was installed?

================================================== ==
Selectron - I'm not feeling well and usually when I'm not, I can't do "technical data" that good. I've saved out your PDFs (very thankful for them cause they are clearer than what I have) and I'm gonna print them and review on paper before I use them for testing.

Selectron - Whenever I test DCV on anything with the battery plugged in and the Key turned ON but Engine Off.... is it always ok to ground to the chassis ground before testing the circuit in question with the positive red test lead?

I ask that because I am thinking of just testing EVERYTHING I can touch and writing down what I tested and what DCV I got back, and then afterwards referring to the reference values "indoors in the a/c" all at once.

Is there any way to test with the multimeter (or other device) for a wire that is decayed, rusted, charred, etc...? Is this the same as testing for DCV? It would seem like if I had a wire(s) that was in bad condition, that it would not be capable of carrying sufficient DCV to whatever sensor or circuit board..... or not grounding right etc.. Correct? I just don't want to have to rip wires apart to get the answers and I'm hoping that voltage testing will give me the info I need.

[wiswind]

I put another message in the speed sensor thread just now.
The gear on the speed sensor drives BOTH the electronic part and the cable that goes to the speedometer.
So, if the gear is incorrect, the speedometer will be giving you the wrong reading.
A rough check would be to time how long it takes from mile post to mile post on the interstate, 60 seconds for each mile at 60mph.
Also, see what the odometer reading is...(set your trip odometer to zero as you pass a mile mark) and see how it matches up after 10 - 20 miles......same tenth of a mile position each mile? (just need the first......and then after 10 or so miles.....).

I would expect the electrical part to be correct....but a check of that can be done by reading MPH through the OBDII port with your scanner.

It is normal for a vehicle speedometer to be off slightly.......but more than a couple of MPH is not good (but if it is causing the low fuel economy.....it would be off by a very noticable amount......like VERY noticable).

[Selectron]

Whenever I test DCV on anything with the battery plugged in and the Key turned ON but Engine Off.... is it always ok to ground to the chassis ground before testing the circuit in question with the positive red test lead?

Yes, that's always safe provided you're on the DC voltage range, because the meter's input impedance is so high that in most instances the meter will be virtually invisible to the circuit under test.

That isn't true of the resistance and current ranges though, so after measuring resistance or current it's good to be in the habit of always switching the meter back to its highest DC voltage range, to avoid damaging the meter if you inadvertently apply voltage whilst on the resistance range, or damaging both the circuit under test and the meter itself when in ammeter mode on the current range, because a multimeter when configured as an ammeter is essentially a short-circuit. (More info than you need, but handy to know).

I ask that because I am thinking of just testing EVERYTHING I can touch and writing down what I tested and what DCV I got back, and then afterwards referring to the reference values "indoors in the a/c" all at once.

It won't do any harm, but you will inevitably end up with some measurements which are impossible to interpret because there simply isn't enough detail on the wiring diagrams, such as resistances of sensors, etc. No harm if you want to do it though, and you might just come up with something unexpected.

Is there any way to test with the multimeter (or other device) for a wire that is decayed, rusted, charred, etc...? Is this the same as testing for DCV? It would seem like if I had a wire(s) that was in bad condition, that it would not be capable of carrying sufficient DCV to whatever sensor or circuit board..... or not grounding right etc.. Correct? I just don't want to have to rip wires apart to get the answers and I'm hoping that voltage testing will give me the info I need.

The piece of kit for that job is something called a milli-ohmmeter, but historically they've always been expensive so it's something which isn't seen too often. Standard digital multimeters leave a lot to be desired when measuring low values of resistance, and fail badly when trying to measure resistances of a fraction of an ohm. I can't find the manual for my expensive meter, but the resistance range specification for my cheap meter (£3.99 from the grocery supermarket!) is stated as +/- 1.2% of reading, +/- 2 digits. The problem isn't in the percentage error - I can live happily with a reading of 1.2% above or below actual value - the problem is in the +/- 2 digits.

Let's say we have a resistance which is known to be a precise 0.5 ohms, and I try to measure it with my multimeter, set to its resistance range - the displayed value could be anywhere between 0.3 and 0.7 ohms (only one decimal place on the resistance range), so that has suddenly become a spread of +/- 40% from the actual value! Horribly inaccurate!

The DC voltage range on all digital multimeters has both greater resolution, and greater accuracy, so if I need an accurate measurement of a low resistance then I pass a known value of current through it, measure the resulting voltage, and then calculate the resistance using ohm's law. Simple, effective, and accurate enough for most purposes.

So that inherent inaccuracy is why it isn't a great idea to use a DMM on its resistance range to try to find a bad connection, bad wire, etc. - you simply can't rely on the readings which it will indicate.

Now let's say we have a bad connection or a bad wire which is introducing an extra 0.5 ohms of resistance into a circuit. Is that a problem? Well, it depends on how much current flows in the circuit, because the more current which flows, the more voltage will be dropped across that unwanted resistance.

Example 1: An LED, drawing 20 milliamps - how much voltage will be dropped across the 0.5 ohms resistance?
Voltage = current x resistance, so V = 0.02 amps x 0.5 ohms = 0.01V

So if we use a nominal 12V as our system voltage, we're only losing 0.01V across the bad connection, so the LED would still receive 11.99V, the LED would work just fine, and we wouldn't even be aware that we had a bad connection, or bad wire, etc.

Example 2: A headlamp, rated at 60 watts, and drawing 5 amps - how much voltage will be dropped across the 0.5 ohms resistance?
Voltage = current x resistance, so V = 5 amps x 0.5 ohms = 2.5V

So now we're losing 2.5V across the bad connection, leaving only 9.5V available at the headlamp bulb, which will be noticeably dim and maybe somewhat yellowed.

So you can see that the more current which flows in the circuit, the more critical that extra resistance becomes. In the case of the LED it was completely insignificant, but in the case of the headlamp, it's a major problem.

So what you're looking for is a voltage drop which shouldn't be there - across a splice point for example, or from one end of a length of wire to the other, or across a connector - anywhere where there should be negligible resistance, and therefore negligible voltage drop - if you are able to measure a significant voltage then that means you have unwanted resistance, and the component or device at the far end of the wire will not receive its intended voltage.

You have two choices when measuring voltage drops - direct, or indirect measurement. Say you want to check a splice point - you can find a point upstream of the splice and a point downstream and measure directly across the two points, or you can measure the upstream point with respect to ground, and then the downstream with respect to ground, and then subtract one from the other. So if a direct measurement gave you 0.02V, then an indirect measurement might give 12.17V upstream, with 12.15V downstream, and you can see that subtracting one from the other would give you the same value of 0.02V, so it doesn't matter which method you use. Hope you follow all of that.

[searcherrr]

About to read your post Selectron.

Wanted to shout this out right quick:

What would it take to blow out/ruin a spark plug wire?

Anyone know what the wires should ohm?

Assume that the spark plug cables look fine on physical inspection before answering.

[wiswind]

What comes to mine would be physical damage.....which often is not visible to a visual inspection.
Grasping the wire instead of the boot will damage the internal cable connection to the end connector......
Even with careful handling, they are not intended to be handled a lot, so many disconnect and reconnect cycles can damage them.
Heat breaks them down....
And some wires are better quality......able to take more physical handling and / or better insulation (often not connected to price or brand name).

[searcherrr]

Selectron - I did reread (today) your post and it made a lot of sense actually. It didn't make sense last night cause I was sick, headache, swollen face from sinus' etc... and I should've gone to bed earlier.... but today it made sense and I thank you for explaining those electrical engineering basics.

I don't know what kind of plug wires I have in there now, but I'm betting they are not Motorcraft cause the shop installed them. They were yanked out probably... over the course of the 2 engines installed, and pulled carefully by the boots by me 1 time to recently install the right plugs at the right gap.

Tonight I went to Autozone to get some Duralast Gold plug wires. I don't intend on using them except for ohming a new set. I'd much rather be able to find the reference ohm values in the CD-ROM, but I can't.

Does anyone know what I should OHM for the plug wires and what brands have had success?

Again, I cannot find the resistance information in the Ford CD-ROM and patience is part of the problem. If anyone knows off hand that'd be great to know. I'll keep watching the thread.

[Selectron]

Post # 4, this thread, TD was quoting a resistance of 5,000 ohms per foot. I had a look in the Ford CD for the '95 Escort just out of curiosity, and that states that the resistance should be 7,000 ohms per foot or less, for what it's worth.

[searcherrr]

New Duralast Gold Plug Wires:

22 inches long 8.93 k ohm - kw262
25 inches long 11.30 k ohm - kw215
42 inches long 9.86 k ohm - kw248
19 inches long 32.30 k ohm - kw297
34 inches long 60.30 k ohm - kw299
34 inches long 14.80 k ohm - kw242

It would seem to me that KW297 and KW299 would have too high a resistance to use. What ya'll think???????

I haven't ohm'ed or inspected the old ones yet.